Tunnel kiln ware support



July 9, 1940- w. o. PRouTY TUNNEL KILN WARE SUPPORT 3 Sheets-Sheet 1 Filed June 1, 1937 lNVENTOR Wi\|`s BY u TORNEY Patented July 9, 1940 UNITED STATES PATENT OFFICE 2 Claims.

This invention relates to tunnel kilns, especially for firing ceramic ware.

Continuously operated kilns of this character are now well-known. These kilns are usuallyr provided with full burners, such as oil or gas, to provide heat for the firing zone; this zone is shown in the form of a muffler. The tunnel is extended on both ends of the firing zone to provide a preheating Zone and a cooling zone, so that the ware is rst gradually heated before it enters the firing zone, and is gradually cooled after its exit therefrom.

'I'he ware is usually stacked on appropriate supports upon movable cars or skids, which are advanced at a definite slow rate through the kiln.

In order to obtain uniformly high grade resuits, either for making the biscuit or for glazing, it is essential that the heating of the ware in the firing zone be keptas uniform as possible. This presents some problems when, as is usual, the ware is stacked quite deeply in tiers upon the car or skid, since some pieces are more exposed than others. In orderto overcome this, it has been customary to direct heaters adjacent the lower portion of the stack, the products of combustion being directly introduced into the tunnel. In this way the products of combustion are intended to rise through the ware.

This expedient is still in many respects unsatisfactory. In practice it has been found that the heating is still far short of uniform. The introduction of the products of combustion directly into the tunnel is also undesirable.

It is one of the objects of this invention to obviate these disadvantages. More particularly, this object is attained by utilizing electrical energy as a source of heat supplemental `to the usual fuel consuming sources.

It is `another object of the invention to make it possible to place this supplemental source of heat where it is most effective to equalize the temperature, and particularly by arranging the source on the moving support (such as a skid or car). In this way, the heat actually generated is dependent upon the presence of the support in the heating or firing zone; and there is little wasted heat by radiation, conduction or convection.

It is still another object of this invention to improve in general the construction and operation of tunnel kilns of this character. i

This invention possesses many other advantages, and has other objects which may be made more easily apparent fromA a consideration of one embodiment of the invention. For this pur- (Cl. .2S-142) pose there is shown a form in the drawings accompanying and forming part of the present specification. This form will now be described in detail, illustrating the general principles of n the invention; but it is to be understood that 5 this detailed description is not to be takenin a limiting sense, since the scope of this invention is best dened by the appended claims.

Referring to the drawings: n

Figure l represents a tunnel kiln thatincor- 10 porates the invention,-shown in horizontal section, and a runway associated therewith;

Fig. 2 'is a vertical sectional View of the kiln, the kiln being shortened in order to reduce the size of the figure;

Fig. 3 is an enlarged transverse sectional View taken along plane 3 3 of Fig. 2, but showing the tunnel kiln in use;

Fig. 4 is an elevation of a portion of the runway and a movable ceramic ware support there- 20 on;

Fig, 5 is a fragmentary view illustrating the inside of the kiln passageway; Fig. 6 is a transverse sectional view taken along plane 6 6 of Fig.` 4;

Fig. 7 is a fragmentary view similar to Fig. 8, illustrating the manner in which the electrical connections may be obtained;

.Fig 8 is a detail section taken along plane 8 8 of Fig. 7; v

Fig. 9 is a horizontal sectional view taken along plane 9 9 of Fig. 4; and

Fig. 10 is a diagram illustrating the manner in which a three-phase source of electrical energy may be utilized to energize the electrical 35 heater.

Ihe tunnel kiln is best illustrated in Figs. 1,

2 and 3. Brick work may be provided to form the sides l, 2, and top 3. In this way a central longitudinal passageway 4 is formed through 40 which the runway structure 5 (Fig. l) extends.

. The tunnel kiln may be provided, as is usual, with a firing Zone 6, a preheating zone l, and a cooling zone 8. The heatingY is shown in the present instance as secured by a pair of banks 45 of fuel burners 9, fed with fuel as by the manifolds l. These burners extend from the outside into the horizontal transverse apertures Il in the walls! and 2. The products of combustion are conducted into the chambers I 2 separated 50 from the passageway 4 into the preheating zone 1, so as to transfer some heat to this zone, from the hot products of combustion. But the most intense heat is secured adjacent the burners 9, thus providing the firing zone 6.

The two longitudinal chambers l2 serve as passages for the hot products of combustion around and over the mufe formed by the brick work I3. These gases emerge through the brick checker work I4 into the top longitudinal passageway I5 connecting to the stack 16 (Fig. 2) shown adjacent the entrance region of the kiln.

The firing Zone (i is thus intensely heated by the conduction of heat through the walls I3 of the passageway 4. The products of combustion do not enter into this passageway 4, the heating being accomplished primarily by conduction.

In Fig. 3, there is diagrammatically illustrated a stack of a plurality of layers of ceramic ware I'I arranged on a supporting structure I8 adapted to be moved at a slow rate through the passageway 4.

The runway 5 upon which the supports I8 are moved through the kiln is supported by the aid of the brickwork piers I9 upon which the tunnel kiln as a whole is supported. Thus extending transversely across the lower portion of opening i and anchored within the piers I5 are a plurality of. girders, such as the I-beams 2Q (Figs. 2, 3 and 5). These I-beains in turn support the longitudinal channel members 2l. These channel members are disposed with vertical legs in which are pivotally mounted a plurality of supporting rollers 22. They are quite closely spaced as indicated in Figs. 4 and 5, so as to form a rolling runway for the supports I8.

The structure of these supports may new be set forth. They are in the form of rectangular cars which may be placed end to end and pushed at a slow rate through the tunnel kiln in any appropriate manner, so as to subject the ware stacked thereon to the heating action of the kiln.

The support I8 comprises a bottom plate member or skid Z3 adapted to rest upon and to roll upon the rollers 22. Projecting'upwardly from the skid 23 are a number of. uprights 24, there being six indicated in the present instance. These uprights 24 may be formed of angle irons; and corresponding transverse horizontal angle irons 25 may be provided to form a support for the framework 2t. Upon this framework 26 there may be supported deep layers of refractory material to serve as a heat insulation between the substructure of the support and the interior of the kiln. rilhis refractory material may be in the forni of a plurality of layers of brick 2T.

As illustrated most clearly in Fig. 3, this brick work 2'! forms the bottom wall of the passageway il while the support I3 is disposed therein. Upon the top of the material 2 may be disposed the racks or other supporting elements upon which the ceramic ware I'I is stacked.

It is essential that during the firing operation, that is. whilethe support I8 is moved through the ring zone 6, the heat imparted to the ware I'I should be as uniform as possible. It has been customary in the past to attempt to effect this result by directly burning fuel in the lower portion of the passageway 4. In this way it was hoped that the lower portion of the stack of ceramic ware would have suiicient` heat imparted to it to equalize the temperature through the stack. However, it was difficult of attainment because there is no reasonably certain `way of controlling the heating, or distributing it.

By the aid of the present invention, the stack of ceramic ware I'I is heated from below by a supplemental source of. heat. For this purpose a heater is carried by each support I8. For example, the heater may take the form of an electrical heating unit 28 disposed on top of the brick work 21, so as to be in good heat conducting relationship with the top 29 upon which the stack of ceramic ware is disposed. The structure of the heater is shown most clearly in Fig. 9. It may comprise a long helix of resistance wire 30 embedded in the body of the heater 28 and having the two terminals 3l and 32. The body of the heater may be conveniently formed of. a ceramic refractory molded material.

It is thus seen that the supplemental heating can occur only when a support I8 is present within the passageway 4. Furthermore, contacting devices are so arranged that the electrical heaters on the supports I8 are energized only during the presence of the supports I8 in and near the ring zone 6.

For this purpose use is made of a series of bus bars illustrated most clearly in Figs. l, 2, 5, '7, 8 and l0. These bus bars are supported along the sides of the passageway 4 by the aid of the upright supporting members 33. These supporting members may be fastened on one of, the vertical legs of the angle iron 2i. These uprights 33 in turn support a long strip 34 of insulation material, such as Bakelite. Inlaid within this material are the three parallel bus'bars 35, 36 and 31 forming the three mains of a three-phase system and appropriately connected to an external source of electrical energy. These bus bars, as indicated in Figs. l and 2, extend slightly beyond the firing Zone and into the preheating zone 2.

Each. of the movable supports I8 carries a pair of brushes adapted to contact with two of the three bus bars 35, 36 and 31 Yso as to conduct electrical energy to the corresponding heater unit 28. This brush construction is illustrated most clearly in Figs. 4, l and 8. Thus a supporting member 38 of refractory insulation material is fastened to the framework on the support I8; A pair of laminated brush structures 39 and 4D are fastened to the support 38 and are urged resiliently against a pair of the bus bars 35, 36 and 31. As illustrated in Fig. l0, these two brushes 39 and di! are appropriately spaced apart in a vertical direction so that they may contact with a chosen pair of bus bars. Thus the pair of brushes 33 and Ml at the left hand end of Fig. l0 are arranged to contact the bus bars and 3l'. rThe b-rushes 35 and d0 in the center portion of Fig. l0 are arranged to contact with the bus bars 36 and 31. The brushes 39 and All) at the right hand end of Fig. 10 are arranged to contact bus bars 35 and 36. Since there is a succession of supports I8 pushed through the tunnel kiln, the brushes 3S and 50 on each of them may be arranged in succession to correspond with the arrangement shown in Fig. l0, whereby the three-phase load is balanced.

The supports i8 are preferably provided with front and rear bumpers il and 42. They may also be arranged to be guided within the passage II as by the aid of the side bumper strips d3 (Fig. 2). These bumper strips d3 are disposed opposite the bottom frame 2B of the supports.

Immediately above the skids 23 of each of the supports I8, there are provided a pair of longitudinal guard `bars 4d (Figs. 4 and 6). These bars 44 are confined against undue lateral inotion by the guide rails 45 supported uponthe runway 5, as by the upright supports 155.

What is claimed is:

1. In combination with a mufle `fired tunnel kiln having a preheating zone, a hot Zone'and a cooling zone, a ceramic ware support adapted to be moved through the kiln, an electric heater carried by the support, a bus bar supported Within the tunnel, and a contact means carried by the support and cooperating with the bar to supply electrical energy to the heater, said bus bar extending substantially the length of the hot zone, whereby the heater is energized only when the support is Within said zone.

2. A ceramic ware support for use in a tunnel kiln, comprising a super structure, and a skid with a at lower surface, said superstructure including a frame mounted on the skid and supporting a body of refractory material, and heating means supported by said body near its upper surface. i

WILLIS O. PROUTY. 

